Light-weight boom parts are an important prerequisite for meeting the requirements for mobile working machines, such as work platforms, cranes, concrete pumps etc. with regard to large load-bearing capacity, large boom length and long reaches. By means of a lightweight construction, these performance data can be improved in comparison to conventional designs, without increasing the total weight of the machine or unfavorably shifting the center of gravity. For example, in the case of mobile cranes, mobile work platforms and mobile concrete pumps, the negative effects of the weight of the boom on the vehicle size and weight, the support base, the number of axles and the needed counterweights can be kept small.
Monolithic designs using fiber-plastic composites (FKVs) like those used e.g. in aeronautics and space travel, are one possibility for implementing this kind of lightweight construction. They are indeed very light, but for financial and safety considerations they are not suitable for the construction of mobile working machines. The production of box girders in a monolithic composite fiber design is very cost-intensive, owing to the complicated fiber structure for force transmission or bearings. In addition, monolithic FKVs are sensitive to impacts, so that they are not suitable for use on a construction site, in building machines such as cranes.
One alternative to a pure FKV design is to use a hybrid construction which combines metallic materials with FKVs. A boom using this hybrid design is known from EP 0 968 955 A2.
The present invention is directed to improvements to a boom of the kind specified above so that the reinforcing layer can be tailored precisely to the particular application, wherein the job-site utility in particular, and thus also the safety are to be increased.